Seismic performance improvement of underground frame structures by changing connection type between sidewalls and slab

Abstract

Seismic failure mechanism of underground frame structures presents that the collapse of underground structures attributes to the insufficient seismic resistance of central columns. Therefore, researches have been conducted to improve the seismic performance of underground structures by enhancing the loading-carrying capacity of the central columns or decreasing the seismic loads transmitted to central columns. For this purpose, this study proposed a new approach by changing the connection type between sidewalls and slab: setting shock absorbing gap (SAG) between sidewalls and ceiling slab, which aims to decrease seismic loads transmitted to central columns. The proposal and working mechanism of SAG were illustrated detailedly. Afterwards, nonlinear finite element models, in which a developed elastoplastic constitutive model was used to simulate the 3D strength and softening behaviour of surrounding soils, were built for simulating the static and dynamic responses of underground structures. Based on the numerical results, SAG affecting the internal forces of structural components before earthquakes were discussed firstly. Then the seismic efficiency of SAG updating the seismic performance of underground frame structures was analyzed by discussing earthquake-induced damage mode of overall structures, soil pressure on structures, earthquake-induced deformations and internal forces of structural components. Finally, the seismic performance of underground frame structures influenced by the width of SAG and frictional coefficient of the sliding surface was investigated, and advice for reasonably using SAG was suggested.